Packaged integrated circuits are continuously shrinking in thickness to fit smaller form factor electronic devices. As a result, the packaging substrate is shrinking in thickness, which reduces the stiffness of the packaging substrate. During manufacturing processes that apply heat to the substrate such as, for example, solder reflow, the substrate may warp. The warpage may be due to stress applied to the packaging substrate from differences in coefficients of thermal expansion between materials in the packaging substrate. When the packaging substrate warps, no-connects between the packaging substrate and the attached die may occur, resulting in electrical failure of the packaged integrated circuit.
FIG. 1 is a cross-sectional view illustrating die non-connects resulting from substrate warpage in a conventional packaged integrated circuit. A packaged integrated circuit includes a packaging substrate 102 having a packaging connection 104. A die 112 is coupled to the packaging connection 104 through a packaging connection 114. When the packaging substrate 102 warps during manufacturing the packaging connection 104 may become disconnected from the packaging connection 114 in portions of the packaging integrated circuit.
Additionally, during packaging of the integrated circuit, the packaging substrate has openings in a solder resist layer exposing contact pads of the packaging substrate. The openings are present in the packaging substrate before attaching the die to the packaging substrate. As a result, the contact pads of the packaging substrate are exposed to atmosphere during manufacturing processes such as heating, reflow, and deflux. High temperatures in these manufacturing process degrade the contact pad through oxidization, which reduces the reliability of electronic connections made to the contact pad.
Thus, there is a need to more reliably package integrated circuits using thin substrates.